1. Field of the Invention:
The present invention relates to an amphibious, all terrain type vehicle (ATV), namely a marsh or swamp craft of the type having two spaced-apart elongated pontoons, and more particularly to an improved tracked amphibious marsh vehicle utilized for travel over different types of terrain, such as swamps, marsh and the like, and for travel cross-country with obstacles of different character, with various degrees of inclination and at relatively high operating speeds of, for example, twenty miles per hour.
2. General Background
Various amphibious craft and all terrain vehicles are known in the art. One commonly known and cited is U.S. Pat. No. 2,546,523, issued March 27, 1951, to Reynolds. The Reynolds patent describes a marsh buggy vehicle with a pair of spaced, elongated pontoons disposed and secured in a parallel relationship, two endless roller chains passing about each pontoon over sprockets mounted on transverse, driven shafts. The chains are joined together transversely by slats which form the treads or cleats for the craft. This type of marsh craft having spaced pontoons have enjoyed substantial commercial success as personnel carriers, and supporting working "uppers", such as draglines for construction of ditches, levees, etc. in a marsh environment. The spaced-apart, tracked pontoons enable the vehicle to turn easily, in a manner comparable to land-based tracked vehicles such as bulldozers and tanks, for example. However, the pontoons provide buoyancy to allow the vehicle to float when crossing open water.
An improved example of the Reynolds type of pontoon marsh vehicle is shown in U.S. Pat. No. 3,842,785, issued Oct. 22, 1974, to Rivet. The Rivet apparatus included two connected pontoons, with two endless drive chains carried in channels disposed on top and bottom of each pontoon. Cleats attached to the chains have plastic blocks which are secured to the web of the cleats and which are positioned to bear against the top and bottom of the pontoons such as when the machine hits a tree stump, thus preventing a bending of the cleats. A series of spaced, transverse I-beams and bulkheads in the bottom of the pontoon hull reinforced the pontoons for work in a treed swamp environment.
These and other similar vehicles using spaced-apart pontoons and roller chain have a number of operating problems, the most common of which is roller chain wear. In operation, the chain is exposed to abrasive mud and sand as well as water. In order to prolong the chain life, it is a common practice to lubricate the elements of the chain in places of connection. Any lubricant applied to a chain has a tendency to catch and collect dirt and sand, which causes rapid wear of the chain elements, particularly between the carrier roller and pin. Roller chain experiences substantial heat build-up at speeds greater than a few miles per hour (eg. 0-5 mph). Thus, roller chain machines are generally slow moving dinosaur-like monsters, typically most effective as work oriented machines supporting a crane, dragline, backline or the like where speed is a minimal need.
Some inventors have used rubber belts instead of metal chains, as for example in U.S. Pat. No. 3,217,687, issued Nov. 16, 1965, to Erkelson et al., which describes vehicle having a float-like body above the tracks provided for operation mainly in water when the drive belts are substantially submerged.
But some vehicles face another problem when traveling on the ground, this problem being commonly known as "chain throw" or "track throw," which arises from the inability of many such designs to provide efficient means for securing a chain or a belt in its place over the driving sprockets or wheels.
Additionally, many "marsh buggies" have had the problem of "track sag," which further adds to the problem of track throw.
These problems have been known in the art for along period of time and, to prevent rapid wear of the elements, a number of solutions have been suggested. In some cases, special pads are attached to the sides of a chain in order to reduce friction and thus to eliminate the problem. While these and other solutions have proven to be satisfactory to some extent, they sill have not provided full reliability.
A recent patent directed to an improved tracked, amphibious vehicle with track securement and guide means is U.S. Pat. No. 4,433,634, issued to John B. Coast, applicant herein. The Coast '634 patent provides a pontoon type amphibious vehicle using bogie wheels and an endless driven belt. The belt carries cleats and sprockets drive the belts. A belt retention system includes lugs on the inner surface of the belts which are located to prevent the belt from moving off its longitudinal center by engaging the inner surface of the bogie wheels. The present invention provides an improvement to the vehicle shown and described in the Coast U.S. Pat. No. 4,433,634 which is incorporated herein by reference.
Other prior patents showing exemplary amphibious type vehicles are listed below:
______________________________________ U.S. Pat. No. Patentee(s) Issue Date ______________________________________ 2,068,664 J. A. Dorst 01/26/37 2,404,489 J. M. Hait 07/23/46 2,487,397 B. A. Swennes 11/08/49 3,108,564 H. L. Prosser 10/29/63 3,299,849 A. H. Pitchford 01/24/67 3,418,961 F. B. Gregg 12/31/68 3,474,751 M. E. Hebert 10/28/69 3,487,802 L. H. Roy 01/06/70 3,611,979 M. E. Hebert 10/12/71 3,760,763 A. V. Brusacoram 09/25/73 ______________________________________